Process for selective extraction of alkaloid



June 30, 1964 J. STALEY ETAL 3 Sheets-Sheet 1 Filed March 7, 1963 June30, 1964 J. STALEY ETAL 3,139,435

PROCESS FOR SELECTIVE EXTRACTION E ALKALOID Filed March 7, 1963 3Sheets-Sheet 2 o. I 5 E 0.1 2 u, E S 2 005 Z 0 IO 5o 60 Mg. H O per Ml.MEK.

N I m 0 IO 20 30 40 5o Mg. H O/ MLMEK.

June 30, 1964 STALEY ETAL 3,139,435

PROCESS FOR SELECTIVE EXTRACTION OF ALKALOID Filed March 7, 1963 3Sheets-Sheet 3 DECANTER AN HYDROUS SOLVENT WATITIR SOLVENT STORAGE BRINESTORAGE NOLLOVHLXB HCI REFRIGERATION UNIT United States atent 3,139,435PRUCESS FQR SELECTIVE EXTRAQTKGN F ALKALGID John Staley, Richmond, andAllan liellerby Clarke, Midlothian, Va, assignors to Philip Morrisincorporated,

New York, N.Y., a corporation of Virginia Filed Mar. 7, 1963, Ser. No.263,637 8 Claims. (Cl. ass-2st This invention relates to extraction ofnicotine and other alkaloid fractions from tobacco. More particularly itrelates to extraction of such fractions without materially affecting thenon-alkaloid constituents of the tobacco and accordingly providestobacco which is substantially unaffected in composition, save for theremoval of nicotine and other alkaloids therefrom. The invention alsoprovides substantially pure nicotine and other alkaloid fractionsessentially free from contamination by fats, waxes, sugars and otherrelated tobacco constituents.

Nicotine and other alkaloids occur in tobacco in both the free andcombined states and are readily extractable in common organic solvents,as are a number of other tobacco constituents. It is to be understoodthat references in this specification to nicotine and alkaloids includenicotine and alkaloids in their salt form.

Solvent extraction of tobacco to remove nicotine has long beenpracticed. Such methods have been characterized, however, by a number ofattendant disadvantages, principally that solvent-soluble tobaccoconstituents other than nicotine are removed thereby, yielding nicotinein admixture with substantial amounts of undesirable impurities andproviding tobacco of markedly inferior character as a result of theremoval of desirable tobacco con stituents.

In United States Patent 3,046,997 to John D. Hind a process forselective extraction of alkaloid fractions from tobacco is set forth,which process overcomes many of the disadvantages inherent in priorprocessing for removal of nicotine from tobacco. Briefly, that processentails extraction of tobacco with organic solvent which is saturatedwith non-alkaloid tobacco constituents, contacting the resultantalkaloid-laden solvent with aqueous brine having an acid pH to transferthe alkaloid selectively from the solvent to the brine, and recyclingthe alkaloidrelieved solvent to the same or other tobacco. Alkaloid isrecovered from the brine by rendering the brine alkaline, extractingwith solvent, and distilling oil the solvent from the extract. Thepresent invention constitutes an improvement over the process of thepatent.

A particular advantage of the present invention in one aspect is theprovision of a markedly simpler and less expensive means for removingnicotine from the brine following contact with the alkaloid-ladensolvent. Nicotine is removed from the brine to permit recycling of thebrine and its repeated use to remove nicotine from alkaloidladensolvent. The nicotine so recovered is, in addition, a valuable item ofcommerce.

Our method of nicotine removal is based on the discovery that a phaserelationship develops between nicotime and salt brine as a function oftemperature. We have further found that the capacity of the brine fornicotine increases as temperature of the brine-solvent system islowered. We prefer a temperature substantially below room temperature,preferably below about 10 C., for transfer of nicotine from solvent tobrine. The lower operative limit of temperature is that at whichfreezing or separation of contained solids occurs. The economic cost ofrefrigeration may constitute a limiting factor on the temperature whichis employed; a suitable low temperature may readily be selected by oneskilled in the art in accordance with the teachings herein contained.

Efiiciency of alkaloid transfer from the solvent to the brine alsoimproves markedly as the pH is lowered. In FIG. 1 there is shown theequilibrium relationship between nicotine concentration in a methylethyl ketone (MEK) saturated aqueous NaCl brine system at 25 C., and itwill be observed that reduction of pH markedly increases efficiency oftransfer of alkaloid from solvent to brine. At pH 7, roughly equalconcentrations of alkaloid are found in the solvent and the brine atequilibrium; acidification to pH increases substantially the proportionof alkaloid in the brine. Below pH 5, and particularly below pH 4,virtually all the alkaloid is transferred to the brine. Since thesolvent, following contact with brine, is to be recycled and shoulddesirably have a nearly neutral pH during extraction of tobacco,however, it is economically disadvantageous to bring the pH of thesolvent-brine system to very low limits since the pH of the solvent mustagain be raised prior to extracting further tobacco. We accordinglyprefer a pH below about 6.5, a pH below 4 being more preferred.

In accordance with the present invention in one embodiment, the pH ofthe alkaloid-laden solvent, which is desirably nearly neutral followingextraction of tobacco, is reduced and the solvent is chilled to a ternerature substantially below room temperature before contacting thesolvent with the brine. Since we prefer to employ a counter-currentextraction column for contacting the alkaloid-laden solvent with thebrine, and since the volume of solvent passing through the column is asa matter of operating efficiency preferably substantially greater thanthe volume of brine passing through the column, the alkaloid-laden brineemerges from the extraction column at a low temperature and an acid pHafter contact with the solvent. An effluent brine pH of about 4.5 and atemperature of about 10 C. are illustrative of the operating conditionsin one embodiment of this invention. Alternatively, refrigeration meansmay be provided in the vessel or column in which the solvent and brineare contacted. The important feature is the lower temperature of thebrine-solvent system; the manner of obtaining such lower temperature islargely a matter of choice.

Under these transfer conditions of low temperature and acidic pH,efficient transfer of alkaloid from solvent to brine is obtained, andthe alkaloid, together with any trace amounts of tobacco solubles,exists as a single phase with the brine. Upon warming the resultantalkaloidladen brine, the nicotine separates into a distinct phase orlayer floating atop the brine and may readily be separated therefrom bysimple decantation or equivalent physical means.

The invention in this aspect accordingly provides an improvement in acontinuous process of tobacco extraction and alkaloid recovery andincludes the steps of contacting the alkaloid-laden solvent with brineat a temperature substantially below that at which alkaloid isultimately recovered from the brine and at a pH below about 6.5. Theresultant alkaloid-enriched brine is thereafter warmed to a temperatureat which an alkaloid phase separates from the brine and the alkaloidphase is physically removed from the brine, as by decantation.

The alkaloid-relieved brine, i.e., warmed brine from which the alkaloidphase has been separated contains only a minor amount of alkaloid;although saturated, the alkaloid concentration is very low, e.g., lessthan 1 mg./ml. of brine. When its temperature is lowered, as by contactwith cooled alkaloid-laden solvent, however, the capacity of thealkaloid-relieved brine for alkaloid increases. At this lowertemperature (below that at which alkaloid is ultimately recovered fromthe brine) the increased capacity of brine for alkaloid permits transferof alkaloid from solvent to brine. The acidic pH of the solvent (whichis preferably lower than the pH of the entering brine) causes a decreasein brine pH, and the acidic environment enhances transfer of alkaloidfrom solvent to brine. An acidic environment may, of course, be providedby acidifying the brine rather than the solvent, or acidification may beaccomplished by adding acid or acidic material directly to the vessel orcolumn in which the solvent and brine are contacted. The particularmeans of providing an acidic environment are not of especial importance.

We prefer to raise the pH of the alkaloid-enriched brine to a nearlyneutral level, suitably 5.5-8, prior to decanting the alkaloid, but thestep of neutralizing the brine is optional and may in addition takeplace either before or after the cold alkaloid-enriched brine is warmed.Somewhat greater amounts of alkaloid are recovered from the brine at ahigher pH.

It will readily be appreciated that our improved process, which in thisaspect permits simple physical separation of nicotine from brine withoutthe need for more cumbersome processes such as solvent extraction andthe like, offers a distinct advantage over prior processes.

We have also found that the efficiency of the process disclosed in theHind patent is improved by maintaining the pH of the extracting solventnearly neutral and preferable slightly on the acid side. A suitablerange of pH is about 5.5 to about 8, with a preferred range being fromabout 6.0 to 7.0. Extraction efiiciency is also improved by use of warmor hot solvent, but care should be taken to avoid extractiontemperatures which can cause damage to the tobacco leaf. We prefer anextraction temperature of about 85 C. or less. For solvents boilingbelow this temperature we prefer an extraction temperature slightlybelow the boiling point of the solvent extraction medium (e.g., about 75C. for MEK, which has a boiling point of about 79.6 C.). Use of apressurized system of course permits employment of a temperature abovethe solvent boiling point.

The data in the following table demonstrate that at a constanttemperature, efiiciency is improved by a less acid pH and that atconstant pH, efiiciency is improved by increased temperature (data forMEK and bright leaf tobacco).

Minimum gallemperlons solvent to atnre, pH extract 90% of C. thenicotine from 18 lbs. tobacco We have further found that efficiency ofalkaloid extraction is related to the moisture content of the extractingsolvent. Surprisingly, virtually no alkaloid is removed from tobaccoupon extraction of dry tobacco with anhydrous solvent. The amount ofalkaloid removed by solvent extraction increases with increasing themoisture content up to a certain point and then, again unexpectedly,decreases.

FIG. 2 is a graph setting forth the relationship between the moisturecontent of the system and the amount of nicotine extracted. The graph isbased upon equilibrium data obtained by extracting 25 g. bright leaftobacco found by analysis to contain 1.48% of alkaloid with 1250 ml.MEK. As shown in FIG. 2, efiiciency of nicotine extraction increaseswith increasing moisture content in the system up to a point, and thendrops off rapidly to a significantly lower level.

The relationship between moisture content of the extracting solvent andamount of nicotine extracted, such as that shown in FIG. 2, exists forall common organic solvents. While FIG. 2 is based upon MEK extraction,other solvents may be employed, as set forth in the Hind patent, and theoptimum moisture content for a given .l solvent under particularextraction conditions can readily be ascertained by one skilled in theart.

The moisture content of the extracting solvent is influenced by themoisture content of the tobacco being extracted, and also by theconcentration and composition of the brine. Adjustment of solventmoisture level is most conveniently effected by addition of water oranhydrous solvent to the extraction solvent. While, as shown in FIG. 2,optimum moisture content may be expressed in terms of mg. H O per m1. ofsolvent, the numerical value of this measure for various solvents can bequite different.

We have found, however, that the moisture content of the tobacco, withwhich the solvent is in equilibrium, is about the same for optimummoisture contents of a wide variety of solvents. Thus we prefer asolvent moisture content corresponding to at least about 10% moisture inthe tobacco being extracted. Levels below about 10% are preferably to beavoided due to low extraction efiiciency, while levels above about 25%are preferably to be avoided because of less than optimum efiiciency andbecause bleeding (i.e., loss of water-soluble tobacco con stituents) orother injury to the tobacco becomes objectionable at moisture levelssignificantly above 25%.

In FIG. 3 there is shown the equilibrium relationship between moisturein tobacco and moisture in extracting solvent at 23 C. (data obtainedwith 1250 ml. MEK and 25 g. bright leaf tobacco). By comparison of FIG.2 and FIG. 3 it will be seen that a tobacco moisture content betweenabout 10%-25% provides a solvent moisture content in the optimum rangefor extraction of nicotine.

An illustrative embodiment of the invention is shown in FIG. 4, which isa schematic flow sheet showing an arrangement of apparatus suitable forpracticing the invention. It is to be understood that various changesmay be made in the system illustrated and that the flow sheet is not tobe taken in a limiting sense.

There are provided a plurality of suitable receptacles 1, which may behogsheads, to contain tobacco from which alkaloid is to be extracted.Preferably, these are equipped with warming means, such as steam heatedcoils within the containers. In FIG. 4 there is illustratively shownsteam admitting means 2 and condensate returning means 3, and there mayalso be provided means such as a temperature sensing device 4 located inan efiluent solvent line in operative connection with an automatic valve5 located in the steam admitting line to afford regulation oftemperature by controlling the amount of steam admitted responsively tothe temperature of effiuent solvent. A tobacco density as great as about15-20 lbs./ cu. ft. is suitable and advantageous, reducing size and costof the equipment and decreasing solvent hold-up, as well as increasingextraction efficiency and facilitating heat transfer. System materialswhich adversely affect tobacco, e.g., copper, should be avoided; glass,stainless steel, porcelain and other preferably inert materials aredesirably employed.

Alkaloid-relieved solvent, which is saturated with nonalkaloidsolvent-soluble tobacco fractions from previous extraction of the sameor other tobacco is drawn from solvent storage tank 6 and pumped toreceptacles 1. Alternatively, fresh or make-up solvent may be employed,i.e., solvent which has not previously been employed for extraction, inwhich event it will become saturated with solvent-soluble tobaccofractions as it passes through the successive receptacles 1 of tobacco.Pump means such as that indicated illustratively at 28 betweenreceptacles D and E may be included in the system as desired.Advantageously, the solvent may pass through the tobacco containersserially, but provision may be made for feeding solvent from tank 6directly to more than one of the tobacco containers, and provision mayalso be made for cycling solvent from one or more tobacco containersdirectly to the subsequent process operations without passing suchsolvent through additional batches of tobacco.

The latter arrangement is particularly useful when employing a solventwhich has not previously been used for extraction of tobacco and whichaccordingly is not saturated with non-alkaloid tobacco fractions.

It is also desirable to contact the solvent with the several batches oftobacco in countercurrent flow. Preferably, in a continuous process, afresh hogshead of tobacco will replace the receptacle designated A inFIG. 4, displacing the receptacle of longest residence in the system (Fin FIG. 4), which may then be processed for recovery of residual solvent(not shown).

The solvent drawn from the storage tank may have a nearly neutral pH,suitably about 6.5. As many varieties of tobacco contain organic acidsand other acidic constituents, it may be desirable to provide means foradjusting the pH of the extracting solvent, should it become more acidicduring extraction, to maintain a generally constant level of pH. To thisend, a tank 7 of alkali, such as KOH or other acid-neutralizingmaterial, may be provided, communicating through appropriate valve meanswith a line of solvent which is to be used for further extraction.Preferably, such arrangement may be in combination with pH sensing means8 located in a solvent efliuent line downstream from and in operativeconnection with automatic valve 9 to admit controlled amounts of alkalito the stream of solvent for maintaining pH at a desired level or withina desired range.

The moisture content of the extracting solvent may, as heretoforedescribed, be ascertained by measurement of the moisture content of thetobacco being extracted. Adjustment of solvent moisture may beaccomplished by addition of controlled amounts of water from tank 26 orof anhydrous solvent from tank 25, as may be appropriate; lessconveniently, adjustment may be etfectuated by altering theconcentration or composition of the brine.

Alkaloid-laden solvent passes from the extraction zone through a heatexchanger 10, which it leaves at a temperature lower than that at whichit entered. In one embodiment of the invention the warm solvent mayenter the heat exchanger at about 70 C. and leave at about 45 C. The pHof the solvent stream is then decreased by addition of acid such as HCl.Preferably, pH sensing means 13 downstream from the point of additionmay be employed to control the admission of acid through valve 12, withwhich such sensing means is in operative connection. A pH below about6.5 is preferred, and a pH of about 4 or below is more preferred.

The solvent is then passed through a chilling unit 14, cooled byrefrigeration unit 15. Acidification may take place after chilling, butin such event allowance should be made for increase in temperature uponaddition of acid. In any event care should be taken to avoid separationof any part of the solvent solution by reason of too low a temperature.An efiiuent temperature of 5-10 C. is suitable.

The chilled and acidified alkaloid-laden solvent then passes through aliquid-liquid extraction column 16 against brine, preferably incountercurrent flow. Suitable brines are set forth in the Hind patent.In an efficient system, a very much greater volume of solvent than ofbrine will pass through the column, and the efiluent brine willtherefore have a temperature and pH only slightly higher than has theentering solvent. Efl luent solvent from the extraction column is cycledto the heat exchanger, whence it may have a temperature of about 35 C.and a pH of about 4.0. Before reaching solvent storage tank 6, the pH ofthe solvent may be adjusted to the level desired for extraction, as byaddition of alkali from tank 7. pH sensing means 23 and automatic valve24 may be em- 6 ployed for adjustment in a manner such as thatpreviously described.

Effiuent alkaloid-laden brine from column 16 comprising water, salt,alkaloid and perhaps a minor amount of non-alkaloid tobacco solubles,all as a single phase, is then passed through heat exchanger 17 andwarmed at least to a temperature at which the nicotine fraction of thebrine separates into a distinct and separate phase. Generally, a greateramount of nicotine will separate as the temperature is increased, but noparticular advantage is obtained by increasing the temperature muchabove the ambient, i.e., about 25 C. The pH of the warmed brine is thenincreased to a nearly neutral level, suitably about 6.5, a tank 19 ofalkali and pH sensing means 18 in operative connection with automaticvalve 20 being desirable. Adjustment of pH may precede the warming step,if desired. The nicotine floating atop the brine is then tapped off indecanter 21 and collected in pool 22. Alkaloid-relieved brine isrecycled to column 16.

It will be evident that changes may be made in the foregoing descriptionwithout departing from the invention. In particular, optional featuresand controls may be omitted, and other features may be added.

We claim:

1. In a continuous process for selective removal and recovery ofalkaloid from tobacco which includes the steps of extraction of tobaccowith organic solvent, contacting the resultant alkaloid-laden solventextract with brine to remove alkaloid selectively from said extract,recycling the alkaloid-relieved solvent to tobacco, recovering alkaloidfrom the brine and recycling the alkaloidrelieved brine for contactingwith further alkaloid-laden solvent, the improvement which comprisescontacting the alkaloid-laden solvent with the brine at a temperaturesubstantially below that at which alkaloid ultimately is recovered fromthe brine and at a pH below about 6.5, thereafter warming the resultantalkaloid-enriched brine to a temperature at which an alkaloid phaseseparates from the brine, and effecting physical removal of the alkaloidphase from the brine.

2. A process according to claim 1 wherein the temperature at which thesolvent and brine are contacted is below about 10 C.

3. A process according to claim 2 wherein the pH at which the solventand brine are contacted is below about 4.0.

4. A process according to claim 1 wherein the pH of thealkaloid-enriched brine is increased to between about 5.5 and about 8prior to recovery of alkaloid therefrom.

5. A process according to claim 1 wherein the tobacco is extracted withorganic solvent at a pH between about 5.5 and about 8.

6. A process according to claim 1 wherein the solvent employed forextraction of tobacco contains moisture in an amount effective toenhance the extraction of alkaloid from said tobacco.

7. A process according to claim 6 wherein the moisture content of thetobacco is at least about 10%.

8. A process according to claim 7 wherein the moisture content of thetobacco is between about 10% and about 25%.

References Cited in the file of this patent UNITED STATES PATENTS802,487 Wimmer Oct. 24, 1905 1,196,184 Villiers-Stuart Aug. 29, 19161,577,768 Smith Mar. 23, 1926 2,525,785 Feinstein et al. Oct. 17, 19503,046,997 Hind July 31, 1962

1. IN A CONTINUOUS PROCESS FOR SELECTIVE REMOVAL AND RECOVERY OFALKALOID FROM TOBACCO WHICH INCLUDES THE STEPS OF EXTRACTION OF TOBACCOWITH ORGANIC SOLVENT, CONTACTING THE RESULTANT ALKALOID-LADEN SOLVENTEXTRACT WITH BRINE TO REMOVE ALKALOID SELECTIVELY FROM SAID EXTRACT,RECYCLING THE ALKALOID-RELIEVED SOLVENT TO TOBACCO, RECOVERING ALKALOIDFROM THE BRINE AND RECYCLING THE ALKALOIDRELIEVED BRINE FOR CONTACTINGWITH FURTHER ALKALOID-LADEN SOLVENT, THE IMPROVEMENT WHICH COMPRISESCONTACTING THE ALKALOID-LADEN SOLVENT WITH THE BRINE AT A TEMPERATURESUBSTANTIALLY BELOW THAT AT WHICH ALKALOID ULTIMATELY IS RECOVERED FROMTHE BRINE AND AT A PH BELOW ABOUT 6.5, THEREAFTER WARMING THE RESULTANTALKALOID-ENRICHED BRINE TO A TEMPERATURE AT WHICH AN ALKALOID PHASESEPARATES FROM THE BRINE, AND EFFECTING PHYSICAL REMOVAL OF THE ALKALOIDPHASE FROM THE BRINE.